1. Field of the Invention
This invention relates to shaft seals and in particular to an improved semi-unitized hub seal.
2. Description of the Prior Art
Shaft seals, including unitized hub seals are well-known in the prior art. Such prior art unitized hub-type shaft seals include a wear sleeve and a sealing element, the two pieces being unitized and one piece press-fitting onto the shaft (or axle) and the other piece having a ridged elastomeric O.D. interference fit into the housing. Such prior art unitized seals are installed by, for example, press-fitting it onto the axle and then installing the wheel hub onto the axle and seal with the elastomeric ridges of the seal sliding into the wheel hub bore. Upon removal of the wheel, the entire unitized seal remains on the axle and can be removed from the axle and the entire seal can be replaced if necessary. The interference fit between the wheel hub and the seal O.D. resists removal of the hub therefrom and additional force must be used in removal of the hub. Other prior art unitized seals are press-fitted into the wheel hub bore (and provide an interference fit on the axle) and the entire unitized seal remains in that wheel hub bore when the wheel is removed from the axle.
Such prior art unitized hub shaft seals are subject to a variety of disadvantages and problems. It is a primary object of the present invention to provide an improved hub-type shaft seal that overcomes various problems in the prior art.
It is a further object of the present invention to provide a semi-unitized shaft seal which is installed as a unit but which, when the wheel hub is removed from the shaft, one seal part stays with the wheel hub and the other part stays on the axle, allowing the wheel hub to be removed from the axle without resistance from the seal.
It is a still further object of the present invention to provide a two-part semi-unitized shaft seal that can be disassembled and each part examined for damage and wear, and replaced separately if necessary, in contrast to the prior art unitized seal which cannot be disassembled for inspection and which must be completely discarded and replaced if one part is damaged or worn.
It is a still further object of the present invention to provide a shaft seal having a sealing lip that runs on a smaller diameter wear surface whereby it will have a longer life than prior art shaft seals having a sealing lip that must run on a larger diameter wear surface.
It is another object of the present invention to provide a semi-unitized shaft seal with a sealing lip that more easily dissipates heat. It is a further object of the present invention to provide a semi-unitized shaft seal with a wear surface which is more accurately concentric than in the prior at shaft seals. It is a still further object of the present invention to provide a semi-unitized shaft seal that does not require an internal gasket, which gaskets are susceptable to being cut or damaged during manufacture and installation. It is another object of the present invention to provide, in certain embodiments, a semi-unitized shaft seal having positive and constant lubrication at the lip without requiring lubricant to go through, for example, holes or passageways to lubricate the sealing lip. It is a still further object of the present invention to provide a semi-unitized shaft seal that does not have metal parts that can interfere with each other during rotation.
It is another object of this invention to provide a semi-unitized shaft seal: that has fewer metal parts, that allows the area directly over where the sealing lip contacts the wear sleeve to be continually flooded with oil to dissipate heat, and that has no area where dirt and water can become lodged or trapped.